1. Field of the Invention
The present invention relates to a test system for adjusting a wireless communication device by impedance loading features, and more particularly, to a test system for reducing time and resources for designing the wireless communication device.
2. Description of the Prior Art
RF (radio-frequency) performance of a wireless communication device determines the communication quality of the wireless communication system. If transmission power of the wireless communication device is not well designed, reception quality of a corresponding base station will be affected. On the other hand, if reception sensitivity of the wireless communication device is not well designed, reception efficiency of the wireless communication device will be affected. In other words, once a defect appears in either Uplink or Downlink, the overall communication quality will be greatly influenced, which may lead to disconnection. Therefore, when designing a wireless communication device, the designer must consider transmitting and receiving performance of an RF circuit in the wireless communication device, in order to achieve the required communication quality.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of an RF circuit 10 of a wireless communication device in the prior art. The RF circuit 10 comprises an RF transmitting module 12, an RF receiving module 14, an antenna switching module 16, an antenna 18, and an antenna matching circuit 20. The RF transmitting module 12 comprises a power amplifier 120 and a matching circuit 122, and is utilized for enhancing power of signals outputted from an RF signal processing unit, so as to emit the signals via the antenna 18. The RF receiving module 14 comprises a low noise amplifier 140, a matching circuit 144, and a surface acoustic wave (SAW) filter 146, and is utilized for receiving wireless signals via the antenna 18, and transmitting the received signal to the RF signal processing unit for performing demodulation, decoding, etc. Generally, when designing the RF circuit 10, a test point TP, taken as a boundary, is connected to a test device with 50Ω impedance to adjust characteristics of the RF transmitting module 12 and the RF receiving module 14 according to a design specification. Then, the antenna 18 is installed in the RF circuit 10, and a network analyzer is utilized for measuring the antenna 18 via the test point TP, so as to adjust a shape of the antenna 18 and the characteristics of the antenna matching circuit 20 to reach an optimal standing wave ratio or reflection coefficient.
After the design of the RF circuit 10 is complete, a wireless communication device installed with the RF circuit 10 is placed in the three-dimensional microwave anechoic chamber for testing total radiation power (TRP) and total isotropic sensitivity (TIS), as shown in FIG. 2. TRP and TIS are used to evaluate the transmitting and receiving abilities of the wireless communication device, and related illustration is as follows.
TRP is the average value of outwardly radiated power of a transmitter in the wireless communication device in omni directional space, which overall estimates the transmitting ability of the transmitter in the three-dimensional space. The testing method of TRP is: set up the wireless communication device to the three-dimensional microwave anechoic chamber as shown in FIG. 2, estimate the effective isotropic radiated power (EIRP) respectively at each 15 degrees interval between the θ-axis and φ-axis on a spherical coordinate system by controlling the location of the wireless communication device, and by carrying out the integral operation on all estimated results, TRP therefore can be obtained. On the other hand, TIS is the receiving sensitivity of the receiver in the wireless communication device in omni directional space, which overall estimates the receiving ability of the receiver in the wireless communication device. The testing method of TIS is: estimate the effective isotropic sensitivity (EIS) respectively at each 30 degrees interval between the θ-axis and φ-axis on a spherical coordinate system by controlling the location of the wireless communication device, and by carrying out the integral operation on all estimated results, TIS therefore can be obtained.
Thus, after the design of the RF circuit 10 is completed, the TRP and the TIS of the wireless communication device are estimated in the three-dimensional microwave anechoic chamber to evaluate the transmitting and receiving abilities of the wireless communication device. After that, the designers may re-adjust the RF circuit 10 according to the estimated TRP and TIS in order to obtain the highest TRP and the lowest TIS conforming to the communication specification. Such designing process, however, takes too much time and resources, and the optimal TRP and TIS may not be obtained with limited time and resource.
In order to improve the above drawback, Taiwan patent application No. 096146318 provides a method and related electronic device for adjusting an RF circuit by impedance loading features, which comprises designing a plurality of test fixtures corresponding to different impedance loading areas according to a predefined operating frequency band, coupling each of the plurality of test fixtures to a test point of the RF circuit for measuring a plurality of RF characteristic sets, and determining an optimal impedance loading area of the RF circuit according to the measured RF characteristic sets in order to adjust the RF circuit. Thus, using the method and related electronic device disclosed in the above-mentioned application, the designers can initially estimate transmitting and receiving abilities of the RF circuit without estimating TRP and TIS in the three-dimensional microwave anechoic chamber, so that time and resources for designing the RF circuit can be reduced. However, as disclosed in the Taiwan patent application No. 096146318, the plurality of test fixtures corresponding to different impedance loading areas are designed in advance, and each test fixtures is coupled to a test point of the RF circuit during testing. Such test method can initially estimate transmitting and receiving abilities, but it takes a lot of time and resources for designing and replacing the test fixtures. Therefore, the prior art cannot effectively reduce time and resources for testing the RF circuit, and thus, the application range is limited.